1. Field of the Invention
The present invention relates to cutting blades that are designed to cut into pavement materials, such as concrete and asphalt. More particularly, the present invention relates to blades that cut grooves into pavement that are wider at the top than at the bottom.
2. Prior Art Description
Most all paved surfaces are impervious to water. Consequently, any low-point or depression in a paved surface has the potential to cause puddling during a rain storm. If the paved surface is an airport runway, for example, such puddling can be extremely dangerous. If the wheels of an airplane roll through a puddle during takeoff or landing, the wheels of the airplane can hydroplane. This can cause the airplane to turn on the runway and/or prevent an airplane from stopping or reaching takeoff speeds prior to the end of a runway.
It is for these reasons that many airports cut grooves into the surfaces of the paved runways. According to U.S. federal safety regulations, runway grooves should be ¼ inch wide, inch deep and should be spaced less than two inches apart. In theory, the grooves provide flow channels for water. Any water on the runway should flow into the grooves and should flow to the sides of the runway. This prevents puddles from forming on the paved surface.
Traditionally, grooves are cut into the pavement of a runway using a standard diamond embossed cutting blade. The cutting teeth on the blade have a uniform thickness. Consequently, when the blade cuts into the pavement it produces a groove that has a rectangular cross-sectional profile.
Grooves with rectangular cross-sectional profiles have sharp edges at the top of the groove. These top edges tend to chip and wear when contacted by airplane wheels, snow plows and other vehicles. Furthermore, wear due to freeze-thaw cycles and other weathering also causes these corners to chip and fall away. The chipped material from the top edge of a rectangular groove falls into the groove, therein causing small obstructions. These small obstructions catch dirt, tire rubber and other debris. Soon, the groove is clogged and cannot effectively channel water. The grooving then becomes ineffective and dangerous puddling can occur.
To prevent grooves from becoming clogged with debris, many airports perform runway cleaning as part of their periodic maintenance schedule. Cleaning removes collected debris from the grooves so that the grooves maintain their ability to channel water. The cost of cleaning runways is substantial in terms of both labor and equipment. Furthermore, the runways of an airport must be periodically closed during cleaning maintenance.
In the prior art, attempts have been made to produce grooves that do not have rectangular shaped cross-sectional profiles. If a groove can be made with sloped sides, then the sharp top edge can be eliminated. This would cause less wear, less debris and therefore would reduce the need for maintenance.
In U.S. Pat. No. 5,311,705 to Zuzelo, entitled Contoured Cutting Tool, a blade is shown having teeth with a triangular profile. Such blades do initially create a groove in pavement that is V-shaped. However, the shape of the cutting teeth causes the cutting teeth to wear unevenly. Consequently, after a short time, the shape of the groove being cut changes and eventually returns to a rectangular shape. The cutting blades must therefore be replaced very often during cutting. Since the blades contain diamond dust and are very expensive, the cost of cutting non-rectangular grooves soon becomes cost prohibitive.
A need therefore exists for a pavement cutting blade that can cut a non-rectangular groove, yet does not wear rapidly. In this manner, shaped grooves can be cut into airport runway pavement in an economically efficient manner. This need is met by the present invention as described and claimed below.